"In a day, the Reach had lost its King, its ruling house and most of its army. Thankfully for everyone, my ancestor Harlen Tyrell had better sense. Until the Maesters sorted out the entail among Mern’s cousins, Harlen the steward was acting Lord of Highgarden. To ensure peace and life in the Reach he would yield the castle to Aegon. The other castles and families would then follow, as they had since the Dawn Age."

According to Olenna Tyrell, Harlen was like most Tyrell men and grew up banging steel too loudly for thought to penetrate, like his descendants Luthor, Mace, and Loras. She also implies that it was Harlen's wife who came up with the idea to surrender to Aegon and convinced Harlen to go along with it.[3]